Method and apparatus for filling a capillary tube with liquid

ABSTRACT

AN EVACUATED LENGTH OF ACCURATELY SIZED BORE CAPILLARY TUBING WITH SEALED ENDS IS SCORED ADJACENT ONE END, SUPPORTED IN A BREAK-OFF MEMBER ON THE OPPOSITE SIDE OF SAID SCORE FROM SAID ONE END, IMMERSED IN A SAMPLE FLUID, AND THE LENGTH OF TUBING PUSHED AXIALLY AGAINST A WEDGE SURFACE OF THE BREAK-OFF MEMBER SO AS TO STRAIN THE SCORE LATERALLY THEREBY CLEANLY BREAKING OFF THE ONE END BELOW THE SURFACE OF THE SAMPLE FLUID. VACUUM DRAWS THE FLUID INTO THE LENGTH OF TUBING WHICH CAN THEN BE CUT INTO ACCURATE SHORT LENGTHS EACH CONTAINING A KNOWN VOLUME OF THE SAMPLE FLUID.

Dec. 14, 1971 s. R. GILFORD 3,626,762

METHOD AND APPARATUS FOR FILLING A CAPILLARY TUBE WITH LIQUID Filed Aug. 12, 1969 2 Shoots-Sheet 1 Inventor SAUL R. GILFORD ATTYS.

Dec. 14, 1971 s GILFQRD 3,626,762

METHOD AND APPARATUS FOR FILLING A CAPILLARY TUBE WITH LIQUID Filed Aug. 12, 1969 2 Sheets-Sheet 8 INVEUTOR SMXW ATTOIUJLYS United States Patent 3,626,762 METHOD AND APPARATUS FOR FILLING A CAPILLARY TUBE WITH LIQUID Saul R. Gilford, Oberlin, Ohio, assignor to Gilford Instrument Laboratories, Inc., Oberlin, Ohio Filed Aug. 12, 1969, Ser. No. 849,371 Int. Cl. G01n 1/14 U.S. Cl. 73-425.6 Claims ABSTRACT OF THE DISCLOSURE An evacuated length of accurately sized bore capillary tubing with sealed ends is scored adjacent one end, supported in a break-off member on the opposite side of said score from said one end, immersed in a sample fluid, and the length of tubing pushed axially against a wedge surface of the break-off member so as to strain the score laterally thereby cleanly breaking off the one end below the surface of the sample fluid. Vacuum draws the fluid into the length of tubing which can then be cut into accurate short lengths each containing a known volume of the sample fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS The basic concept of using length of capillary tubing for the measurement of fluids through the drawing of the fluid into the respective bores of the said lengths is disclosed in co-pending application Ser. No. 472,294, filed July 15, 1965 by the applicant, and entitled Fluid Sample Measuring and Diluting Method and Apparatus, now Pat. No. 3,475,127, dated Oct. 28, 1969.

Two other co-pending applications disclose methods and apparatus for filling a plurality of lengths of capillary tubing with liquids. These are Ser. No. 781,386 filed Dec. 5, 1968 (a continuation-in-part of Ser. No. 741,024 filed June 28, 1968) entitled Apparatus for Sampling Blood or the Like Fluid, and Ser. No. 830,185, filed May 15, 1969 (a continuation-in-part of Ser. No. 803,031 filed Feb. 27, 1969) entitled Apparatus and Method for Filling Capillary Tubing with Fluids.

Application Ser. No. 781,386 contemplates the mounting of a plurality of lengths of tubing in an evacuated vessel, with one end of each length open in the vessel so that when liquid is introduced to the vessel, at the top thereof, the liquid will be drawn into the lengths of tubing.

Application Ser. No. 830,185 relates to a method and apparatus whereby a plurality of lengths of pre-evacuated capillary tubing is mounted in a vessel, with the ends protruding into a well. The liquid to be sampled is introduced into the well, the upper ends of the lengths of tubing being thereafter broken off below the level of the liquid to enable the contained vacuum to draw quantities of liquid into the respective lengths of tubing. These upper lengths are pre-scored to enable clean breaking of the upper ends.

BACKGROUND OF THE INVENTION The field of the invention is micro-sampling and has this in common with all of the co-pending applications. But for the basic application Ser. No. 472,294, the copending applications are primarily concerned with the handling of a plurality of lengths of capillary tubing, although not being limited thereto. The apparatus disclosed for handling a plurality of lengths is, however, not convenient or economical in the event that the technician wishes to work with a single length. Since the type of tubing which is used for sampling is quite fragile, difliculties in handling the same have arisen.

The invention cures these difliculties making it a sim- Patented Dec. 14, 1971 ple matter to fill a single length of capillary tubing for sampling or the like purpose.

The method and apparatus of the invention are applicable to biological and industrial fluids, and suitable for use in general laboratory work in biology, chemistry, industry, for quality control, etc.

As explained in application Ser. No. 830,185 there are considerable advantages in handling lengths of capillary tubing which have the capability of carrying a quantity of fluid greater than that which Can be retained in a vertically oriented length of open-ended capillary tubing. This stems from the fact that empty lengths of capillary tubing are evacuated and their ends sealed. When one end is opened while immersed in a body of liquid, the vacuum draws the liquid substantially fully into the bore of the length of tubing and retains the liquid therein. The filled length does not have to be held in a horizontal position in order to prevent the loss of liquid, and 0bviously does not have to be held horizontally or even slanted downward away from the source in order to fill it, as often is required in conventional handling of openended capillary tubing.

Considering also, the requirement of filling capillary tubing from a body of liquid, one must either tip the vessel to enable the horizontally oriented length of openended tubing to be dipped into its surface, or, a squeeze bulb must be attached with a suitable adapter in order to aspirate the length of tubing while dipping same into the body of fluid. In this latter case, once the length of tubing has been filled, again its handling is difficult because of the need to keep it horizontal. The use of wax plugs in holding liquid in lengths of capillary tubing is not a totally satisfactory technique.

The desirability of handling very small quantities of fluid by carefully cutting accurate short lengths of a longer length of capillary tubing containing the fluid will be understood from the disclosure of the co-pending applications. The invention herein makes it advantageous even in the case where single lengths are being handled in laboratory, testing or quality control work. The invention provides a method and apparatus which will assure easy handling without contamination and with a minimum chance of breakage.

SUMMARY OF THE INVENTION According to the invention, the length of capillary tubing which is to be used is evacuated and its ends flamesealed, thereby containing the vacuum. A score line is made by any suitable device adjacent one end 'of the length. This latter length is immersed into a body of the liquid with which it is desired to fill the length of tubing. In the usual case the container will be a vial or cuvette of some sterile substance such as glass or synthetic plastic of relatively stiff character. In other instances the container may have walls of flexible material.

In the case of a container having stitf walls, a small wedge device is used to apply a laterial strain to the lower end of the length of tubing to cause it to break off below the level of the liquid in the container.

In the case of a container with flexible walls, the user grasps the length of tubing through the walls between his fingers, on opposite sides of the score line and applies the lateral strain to sever the end from the longer length.

In either case, since the end is broken off below the level of the liquid, as soon as the bore is open, the vacuum within the bore draws the liquid into itself substantially filling the bore. The one end being closed, there is no tendency for the liquid on the interior of the length of capillary tubing to run out, and the length is easily handled thereafter as for example, placed in apparatus which will break the same into predetermined shorter lengths. It will be appreciated that these short lengths each will represent some predetermined volume of liquid to be used in micro-sample testing and so on.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary sectional view through a length of capillary tubing installed on a wedge device, shown on an exaggerated scale.

FIG. 2 is a sectional view showing the manner in which the end section of the length of capillary tubing is broken off by pushing down on the length of tubing.

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1 and in the direction indicated.

FIG. 4 is a sectional view similar to that of FIG. 2 but illustrating a wedge device of modified form which is operated by causing relative movement between the flexible end of the wedging device and the fixed end of the length of tubing.

FIGS. 5 and 6 are diagrammatic perspective views showing two steps in the method of practicing the invention using a container with flexible walls.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the invention comprises disposing the scored end of an evacuated length of capillary tubing immersed in a liquid which it is desired to draw into the length of tubing and breaking the scored end from the longer length so that the liquid immediately is sucked into the bore of the longer length.

The problems of holding the length of tubing and immersing the same and breaking the same are solved by the invention as disclosed hereinafter.

In the case of the structures which are illustrated in FIGS. 1, 2, 3 and 4, the container or cuvette is formed of some relatively stiff material, such as glass, methacrylate resins, and the like and in such cases a wedge device is used to achieve the application of lateral strain on the end of the length of tubing. In FIGS. 5 and 6 the container is in the form of a cuvette having walls which are flexible, somewhat like a bag. The liquid is in the container, the length is immersed in the liquid and the technician grasps the length of tubing between his fingers on opposite sides of the score line and manually breaks the tubing below the level of liquid.

The reference character 10 designates generally a length of capillary tubing of glass having a bore of uniform, accurately known diameter and which it is desired to fill with a liquid 12 contained in a suitable vessel 14. The vessel in this case is made of glass or some stiff plastic, as common in the fields of biology, chemistry, hematology and the like. The length of tubing 10 has its ends sealed as by flame sealing as shown at 16 and 18, and when sealed, the hollow bore 20 is evacuated. Just above the lower end 18 as viewed in the drawings, the length of tubing is scored to provide a score line shown at 22, the section between the score line 22 and the end 18 being designated the end section 24. The techniques for flame sealing the ends in vacuum are well-known, and likewise the techniques for scoring are known. In furnishing the lengths of evacuated tubing, the maker may prescore them or leave the user to apply the score line 22 at any desired location.

When it is desired to fill the length of tubing 10 with the liquid 12, a wedge device 26 is fitted over the lower portion of the length 10. The wedge device in FIGS. 1, 2 and 3 comprises a lower block 28 having a slanted or wedge surface 30 and an integral collar 32 providing an interior cylindrical passageway 34. The axis of this passageway intersects the wedge surface 30 at an acute angle and obviously, when the length of tubing 10 is engaged in the passageway as described, it will be coaxial with the passageway 34. The wedge device 26 is preferably made out of molded synthetic resin of some suitable type which is compatible with the liquid 12 and which provides a fair degree of firmness. There are many known plastics which are capable of being used, such as nylon, polyethylene, tetrafluorethylene, etc. The diameter of the passageway 34 is chosen to fit firmly upon the length of tubing but to enable sliding thereof relative to the collar 32 when forced to do so. The neck 36 between the collar and the block 28 in this case should be robust enough to resist substantial bending for a reason presently to be explained.

After the wedge device 26 has been fitted u on the length of tubing 10, it is immersed into the test fluid 12, the length of tubing 10 being pushed downward by the technician using either a small gripping sleeve or his fingers. This causes the length of tubing to slide through the passageway 34 of the collar 32. In the process of this movement, the end 18 moves against the slanted surface 30 and is deflected thereby, applying a lateral strain on the end 18. The collar 32 holds the length of tubing 10 above the score line 22, and the strain is applied below the score line 22 as the length 10 is pushed downward. This lateral strain breaks the end section 24 at the score line 22, and this severed section drops to the bottom of the vessel 14. As soon as the break occurs, the vacuum in the hollow bore 20 draws a quantity of the liquid 12 into such bore and fills the same as shown at 12 in FIG. 2.

After this has occurred, the length of tubing 10 is withdrawn from the liquid 12 carrying the wedge device 26 with it. The wedge device 26 is now discarded and the length of tubing 10 with the occluded liquid 12 may be processed further as disclosed in the co-pending applications, as by dividing the same into shorter sections of known length and hence known volume for use as micro-samples.

FIG. 4 illustrates a modified form of the apparatus of the invention, also for use with a container that is relatively stifl. In this case the container 14' is a relatively shallow cuvette containing a small quantity of sample liquid 12 and the length of tubing 10 is scored at 22 above the end 18 as in the previously described structure. The wedge device 26 in this instance is made of somewhat more flexible material than the device 26 previously described. For example, it could be an elastomer of some type which enables the two functions which provide the lateral strain for breaking off the end section 24.

The collar or handle portion 32 in this form of the apparatus is somewhat elongate so that it is capable of being grasped between the fingers of the technician as shown in FIG. 4. The length of tubing is inserted into the passageway 34' and pushed down against the lower block portion 28' which may have a small seat or depression 29 molded into its slanted or wedge surface 30'. The neck 36' is intentionally narrow and flexible so that when the entire wedge device 26' is pushed downward against the bottom wall of the vessel 14', the block portion 28 will swing to the broken line position shown in FIG. 4. This will apply the lateral strain required to break the end section 24 from the length of tubing. The softness of the material from which the device 26' is molded enables the technician to pinch the handle portion 32' and thereby tightly grip the length of tubing 10 in the passageway 34' so that when the device 26' is pushed downward, there is no relative movement between the length of tubing 10 and the device 26.

The difference between the structures of FIGS. 1, 2 and 3 on the one hand, and the structure of FIG. 4 on the other hand is the movement of the length of tubing relative to the wedge device and fixation of the block and its wedge surface in the one case, and the fixation of the length of tubing and movement of the block and its wedge surface in the other case. In both cases, there is relative movement between a swinging or wedge surface and the end of the length of tubing to apply a lateral strain to such end. In both cases there is a lateral restraint or holding of the length of tubing on opposite sides of the scored line while a bending moment is applied at said score line.

It is feasible to have a combined type of function to effect the breaking off of the end of the length of tubing.

In FIGS. and 6 there is illustrated an application of the method of the invention to a type'of container which has flexible side walls. The container 50 in this case has a cover member or cap '52 of some relatively stiff material, such as synthetic resin of apolymerized type. The body of the container 50 is a flexible bag 54 and the walls are preferably transparent. For example, such bag 50* may be formed of polyethylene or the like. The bag is sealed or thermally welded to the cap 52 and a passageway 56 in the cap enables the technician to insert the lower end of the length of tubing 10 into the interior of the container 50. The bottom end of the passageway 56 may have a flapper valve (not shown) which prevents the liquid 12 in the bag from being contaminated until it is ready to be used. Likewise, or alternatively, the entrance to the passageway 56 may have a pair of closed abutting lips or flaps which may be envaginated by the insertion of the lower end of the length of tubing 10.

The technician holds the cap 52 in one hand as shown in FIG. 5 and inserts the length of tubing 10 with the other hand. When the length of tubing 10 is disposed with a substantial portion of its lower part within the bag it will be self-supporting long enough for the technician to move his hand from the upper end of the length to the lower end as shown in FIG. 6-, this lower end now being grasped through the flexible walls. The very bottom tip, which is identified as 18 is that which is grasped by the right hand as shown in the views. This is below the score line 22. Now the technician can shift his left hand and, cradling the majority of the containers in his cupped hand, with his thumb and one of his forefingers he grasps the length of tubing through the flexible walls above the scored line. With this posture, the technician simply applies the lateral strain needed to break the lower section 24 free below the level of the liquid 12 to cause a quantity to be drawn into the bore of the length of tubing 10. The broken piece 24 will remain in the bottom of the container, and other lengths may be filled in the same way after removal of the respective filled ones.

' The construction of the vessel 50 is not intended to be limiting, but merely to illustrate one type of flexible wall vessel that will enable the lateral strain to be applied manually and without contamination of the sample by the technician or vice versa.

What it is desired to secure by Letters Patent of the United States is:

1. A method of filling a single length of sealed-end evacuated accurately sized bore capillary tubing with a sample liquid and retaining such fluid in the length which comprises:

(A) scoring a transverse line on thelength of tubing adjacent one axial sealed end of said length,

(B) immersing the tubing axially into a quantity of said liquid to a degree bringing the score line below the level of the liquid, said immersing being effected by bringing said one sealed end into a vessel having flexible walls and said quantity of liquid therein,

(C) manually supporting the length of tubing from the exterior of said vessel but through the said flexible walls thereof on axially opposite locations of said scored line and applying a bending moment at said line,

thereby causing one portion of said tubing to break off from the other while so immersed and at least the said other portion to have a quantity of said sample liquid drawn into the hollow bore thereof, the portion of said tubing which is broken 01f being the shorter and including said one axial sealed end.

2. A method of filling a single length of sealed-end evacuated accurately sized bore capillary tubing with a sample liquid and retaining such fluid in the length which comprises:

(A) scoring a transverse line on the length of tubing,

( 8) immersing the tubing axially into a quantity of said liquid to a degree bringing the score line below the level of the liquid,

(C) supporting the length of tubing on axially opposite locations of said scored line and applying a bending moment at said line,

thereby causing one portion of said tubing to break off from the other while so immersed and at least the said other portion to have a quantity of said sample liquid drawn into the hollow bore thereof, said other portion being supported circumferentially and the support of the one portion and the bending moment being provided by moving the said other portion of the length of tubing and a slanted surface toward one another along a line coaxial with the said other portion.

3. The method as claimed in claim 2 in which the said one axial sealed end of the length of tubing is moved against the slanted surface.

4. Apparatus for sampling fluid contained in a vessel which comprises:

(A) a length of evacuated accurately sized bore capillary tubing having sealed ends and a score line adjacent one sealed end,

(B) a break-off member consisting of (i) means for supporting said length circumferentially at a location spaced axially from said score line but opposite to said one sealed end relative to the score line,

(ii) a part having a slanted surface adapted to engage with the said one sealed end in a disposition which would deflect said sealed end if the surface and length of tubing were moved toward one another,

(iii) means enabling relative movement between said length and said slanted surface along a line coaxial with said length whereby to place lateral strain on said one sealed end and apply a bending moment at said score line,

the supporting means and surface being spaced apart a suflicient distance such that the portion of said length of tubing between said score line and one sealed end will be broken away from said length of tubing by said lateral strain while said score line is immersed in said fluid.

5. The apparatus as claimed in claim 4 in which the means for supporting said length circumferentially enables sliding axial movement of said length and the part having the slanted surface is substantially fixed relative to said supporting means whereby the pushing of said length of tubing axially toward said slanted surface through said supporting means will provide said lateral straln.

6. The apparatus as claimed in claim 5 in which the length and break-off member are connected together and adapted to be inserted into said vessel, break-off member first, so that the break-off member can be pushed against the bottom of the vessel while the score line is immersed and continued pushing will result in the breaking of the end section.

7. The apparatus as claimed in claim 6 in which the break-off member is an integral structure, the supporting means comprises a collar, and said part comprises a wedge shaped block spaced below said collar.

8. The apparatus as claimed in claim 7 in which the break-off member is made of molded synthetic resinous material.

9. The apparatus as claimed in claim 4 in which the means for supporting said length circumferentially provides structure for preventing axial sliding movement of said length of tubing and the part having the slanted surface is substantially fiexibly connected to said supporting means whereby the pushing of the break-off member into said vessel will carry with it the length of tubing thereby causing the swinging of the part having the slanted surface against the said one sealed end to apply said lateral strain.

10. The apparatus as claimed in claim 9' in which the break-off member is formed of an elastomeric material to enable the supporting means to be compressed for pinching the length of tubing through said supporting means.

References Cited UNITED STATES PATENTS 7/1942 Booye et al.

128Bl. SAMP. DIG 5 US. 01. X.R.

23-259; 128--2 B, Dig. #5 

